The Icon Handbook

The paperback would make a great gift for the season, but for now it’s only available as digital edition (PDF, ePub & Mobi).
I couldn’t resist the visual goodness and the chance to get inside the mind of one the great designers on this field (Jon designed Firefox’s logo) and rewarded myself with one.

From ideation to drawing tips, web or application icons, this is one of the best references on icon design available, further confirmed by the great feedback on Twitter.